The Chemistry of Wine. 



361 



fermentation, and which has consider- 

 able influence upon the flavor as also 

 upon the taste of wine. This is gly- 

 cerine, a substance which is used to a 

 great extent in chemical operations, 

 and which, for such purposes, is raan- 

 ufactured from palm oil, the residues 

 of soap factories, etc. 



It imparts a peculiar fullness and 

 body to the young wine. But this 

 substance, as well as every other, is 

 dissolved and changed b}' time and fer- 

 mentation, although the process is 

 a very slow one, and it then produces 

 an ether which gives a peculiar, sharp 

 flavor to old wines. The more this 

 flavor increases the more will the 

 fullness and smoothness of the wine 

 decrease, and attempts have been 

 made, frequently, to impart more 

 body to old wines by the addition of 

 glycerine. Such experiments should, 

 however, only be made with glycerine 

 which has been purified by repeated 

 distillations, as the common article 

 of commerce generally contains addi- 

 tions which will impart a disagreea- 

 ble taste to the w^ine. 



We will now consider the changes 

 to which the color of the wine is sub- 

 jected during fermentation. 



The coloring matter contained in the 

 so-called ivhite wines is generally onl}^ 

 oxydized tannin. It is contained in 

 the skins of the berries, and assumes 

 a brown color through the action of 

 the oxygen of the air. The riper the 

 grape, therefore, or the longer it is 

 exposed to the air after gathering^ 

 the dai'ker will be the wine. Of 

 course wo arrive at the same results 

 by fermentation on the skins. 



The coloring matter of red wines is 

 blue when in an isolated condition. 



and becomes red only through the ac- 

 tion of the acids. It is closely con- 

 nected with tannin, which is developed 

 in red wines by fermentation on the 

 husks, stems, and seeds. This con- 

 nection, however, is not advantage- 

 ous, as the tannin is very much subject 

 to change and becomes indissoluble, 

 when it will have the effect to depose 

 the color in the lees, thus partially 

 discoloring the wine. But other cir- 

 cumstances may also serve to reduce 

 the color. Among these we will es- 

 peciallj" mention the contact with sub- 

 stances which contain humus, and 

 which have been decomposed by the 

 action of the atmosphere, and es- 

 pecially b}' the action of heat. They 

 will then discolor the wine. Among 

 these we will name the stems of the 

 grapes, the decomposed skins of 

 the berries, and the storing of the 

 wines in old, badly kept casks. 



If the stems or husks of grapes, 

 which have become browned by the 

 influence of heat and air, are fer- 

 mented with sugar water, the fluid 

 thus produced will discolor red wine. 

 Old, partly decomposed oak wood has 

 the tendency to discolor red wines in 

 the highest degree, and red wines 

 which have been fermented in old oak 

 vats will not be as dark in color as. 

 those fermented in fresh, sound vats. 



Burnt sugar (caramel) has no influ- 

 ence on the color of wines, which 

 is only affected by humus acid. 

 Even the slow change which tannin 

 effects in this respect is produced by 

 a change of the tannin to humus acid^ 

 caused by the slow action of the air, 

 or by a much higher temperature. 



(To he continued.) 



